Size-exclusion simulated moving bed for separating organophosphorus flame retardants from a polymer.

Over 500,000t of flame retardants in electronic wastes are consigned to landfills each year. A room-temperature, size-exclusion simulated moving bed (SEC-SMB) was developed to recover high purity (>99%) flame retardants with high yield (>99%). The SSWD method for ternary mixtures was developed for SEC-SMB. Fourteen decision variables were optimized to obtain the lowest separation cost within 1min. The estimated cost is less than 10% of the purchase cost of the flame retardants. The estimated cost of the optimized SEC-SMB is less than 3% of that of a conventional batch SEC processes. Fast start-up methods were developed to reduce the SMB start-up time by more than 18-fold. SEC-SMB can be an economical method for separating small molecules from polymers.

Method for efficient recovery of high-purity polycarbonates from electronic waste.

More than one million tons of polycarbonates from waste electrical and electronic equipment are consigned to landfills at an increasing rate of 3-5% per year. Recycling the polymer waste should have a major environmental impact. Pure solvents cannot be used to selectively extract polycarbonates from mixtures of polymers with similar properties. In this study, selective mixed solvents are found using guidelines from Hansen solubility parameters, gradient polymer elution chromatography, and solubility tests. A room-temperature sequential extraction process using two mixed solvents is developed to recover polycarbonates with high yield (>95%) and a similar purity and molecular weight distribution as virgin polycarbonates. The estimated cost of recovery is less than 30% of the cost of producing virgin polycarbonates from petroleum. This method would potentially reduce raw materials from petroleum, use 84% less energy, reduce emission by 1-6 tons of CO2 per ton of polycarbonates, and reduce polymer accumulation in landfills and associated environmental hazards.